1. Field of the Invention
This invention relates to a mixing and dispensing assembly that includes a single chamber capsule with a piston that is removable to add a liquid component.
2. Description of the Related Art
A number of mixing and dispensing capsules are known in the art, including capsules for storing, mixing and dispensing dental materials. Many capsules include two initially separate compartments that each hold one component of the desired, final preparation. Capsules for mixing and dispensing dental materials often have a configuration adapted to fit within a holding mechanism of a dental amalgamator that is operable to provide a vibratory motion to mix the components.
Some two-compartment mixing and dispensing capsules have a seal or membrane between the compartments that is ruptured to bring the components into contact with each other. The seal is ruptured either prior to a mixing operation or as a result of the vibratory motion presented by the amalgamator. An example of a mixing and dispensing capsule having a seal that is ruptured prior to the mixing operation is described in U.S. Pat. No. 3,595,439, assigned to the assignee of the present invention.
Certain capsules having two initially separate compartments are not entirely satisfactory, however, for all applications. For example, the liquid component of some preparations may tend to volatilize or diffuse through the seal over an extended period of time. Moreover, the user may desire in some instances to make a preparation having a ratio of the two components which is different from the ratio of the components as packaged.
U.S. Pat. No. 4,972,969, also assigned to the assignee of the present invention, describes a single chamber ampule that is initially provided with a single component, with an additional component or components added to the ampule immediately prior to use. The ampule is placed within a capsule, and the capsule is then secured in a holding mechanism of a dental amalgamator for mixing the ingredients. The ampule has flexible wall portions and may be compressed by finger pressure or by use of a dispenser in order to expel the mixed contents directly to an application site. While the ampule described in U.S. Pat. No. 4,972,969 is satisfactory for many applications, it is desirable in some instances to use a capsule having a piston that is movable upon movement of a lever actuated, ratchet-type dispensing device in order to utilize the mechanical advantage presented by a lever.
Occasionally, mixing of two or more components of a dental preparation is carried out by an end user by transferring the components from a bulk container to a relatively rigid capsule adapted for use with a conventional dental amalgamator. Measured quantities of each component are placed within the capsule, and the capsule is then closed and placed within an amalgamator to shake the capsule and mix the ingredients. Thereafter, a spatula or other device is utilized to remove the mixed contents from the capsule for transfer to the point of use. Such practice, however, necessitates careful cleaning and possibly sterilization of the capsule if the latter is to be re-used. Further, the mixture in the capsule cannot be conveniently applied to the application site without transfer to another tool or dispenser.
One disadvantage in working with preparations made of liquid and powder components is the possibility of displacing a portion of the powder component when the chamber of an amalgamator capsule is closed. For example, part of the powder component may "puff" and be displaced through the opening of the amalgamator capsule as it is closed. As can be understood, loss of a portion of the powder component may result in a preparation that does not have the desired physical or chemical properties.